The present invention concerns a data transmission system comprising a data transmitter and a portable information detection device for receiving the data transmitted by the data transmitter. In particular, the invention concerns such a data transmission system in which the data transmitter includes swept frame display means and a generator composite video signals for controlling the operation of the swept frame display means.
The present invention may be used in the field of the transmission of data from a computer, including a swept frame monitor, and a watch receiver, the invention being described hereafter in relation to this exemplary application to which it is nevertheless not limited.
Data transmission systems such as defined hereabove are already known. Patent application WO 95/15057 in the name of Timex Corporation, for example, describes a system for the transmission of data from a computer to a watch receiver. The monitor is equipped with a video signal generator which effectuates a swept frame of the screen. The data is transmitted to the watch receiver by modulating the luminosity of the screen during the frame sweeping so as to generate light pulses corresponding to the binary information of the data. The watch receiver includes a photo detector fixed on its case for detecting the transmitted light pulses.
However, such a system has a number of inconveniences. Firstly, the photo detector requires a precise orientation with respect to the screen of the swept frame monitor to be able to detect the transmitted light pulses. Such a system also requires the placement of a supplementary element on the exterior surface of the watch receiver, namely the photodetector. This often poses problems during the conception of the wrist watch, taking its small dimensions.
Another problem is related to the fact that the data transmission takes place by a variation in the luminosity of the screen of the monitor. This transmission is likely to be perceptible and thus troublesome to the user.
In addition, the luminosity of the screen may be varied by the user on most monitors available commercially. Due to this fact, the correct transmission of the data by variation of this luminosity is not always achieved by such this system.
Thus, an aim of the present invention is to supply a data transmission system of the type defined hereabove which overcomes or ameliorates the inconveniences of the prior art.
Moreover, an aim of the invention is to supply such a data transmission system whose realisation is simple, viable and not cumbersome.
In addition, an aim of the invention is to supply such a data transmission system whose realisation requires only a minimal number of elements.